The present invention relates to mounting of fuel vapor vent valves in plastic fuel tanks and particularly plastic fuel tanks for motor vehicles.
Presently in passenger cars and light trucks, the fuel tank has a vapor vent valve disposed in the fuel tank and positioned to have the valve inlet located in the vapor dome above the liquid fuel level and the valve outlet connected to a storage device such as a charcoal filled canister for storing fuel vapor when the engine is not running. Such valves are typically installed in the fuel tank through an access opening in the upper wall of the tank which requires adequate sealing of the valve about the opening.
Heretofore, it has been found satisfactory to provide portions of the valve exterior to the fuel tank formed of material compatible with the material of the fuel tank to enable sealing of the valve over the access opening by weldment. However, this technique has the disadvantages of relatively high cost in mass production and rendering the valve non-removable from the tank.
Furthermore, plastic fuel tanks are formed of material which is suitable for exposure to liquid fuel and vapor but which has a prohibitively high permeability to the vapor. Accordingly the tanks are formed with a non-permeable barrier layer embedded in the wall of the tank to minimize the escape of fuel vapor. However, where an access opening is formed in the upper wall of the tank for installation of the vapor vent valve, the barrier layer is broken and an area subject to vapor permeation is created.
It has thus been desired to provide a way or means of mechanically installing, sealing and retaining a fuel vapor vent valve through an access opening in the upper wall of a fuel tank in a manner which provides a simple one-piece assembly, is relatively low in cost and provides positive sealing of the vapor barrier layer in the tank wall.
The present invention provides a technique for positively retaining and sealing a fuel vapor vent valve through an access opening in the upper wall of a plastic fuel tank having an embedded vapor barrier in a manner which seals the vapor barrier layer and also eliminates the need for separate fasteners at installation. The vapor vent valve may be supplied as a subassembly complete with a seal ring and a discontinuous locking ring provided thereon. Portions of the locking ring engage torque transmitting surfaces on the valve to prevent relative rotation therebetween; however, limited axial movement of the ring with respect to valve is permitted to facilitate installation on the tank. At installation the subassembly is inserted through the access opening with the locking ring registered against the exterior side of the access opening. The subassembly is then rotated and the edge of the locking ring engages and feeds through a slit formed in the edge of the access opening; and, upon continued rotation, the locking ring feeds axially completely through the slit until fully positioned within and engaged with the interior surface of the tank wall with portions of the locking ring engaging the exterior of the valve to prevent rotation of the valve once installed.
The valve, seal ring and locking ring may thus form a self-contained subassembly ready for installation and locking in the fuel tank without the need for separate fasteners or tools upon installation on the tank.